Patients with unipolar or bipolar affective disorder (depression) have been shown to have abnormally high nighttime temperatures. We hypothesize that elevated body temperature may be responsible for several alterations in depression such as reduced thyropin secretion. Procedures such as selective rapid eye movement (REM) sleep, total sleep deprivation, and administration of drugs such as tricyclic antidepressants appear to reduce brain temperature. We believe the antidepressant effects of these agents are related to their capacity to reduce brain temperature. Further, direct or indirect cooling of the brain might have antidepressant effects. We will test our hypothesis by cooling the face, which will cool the brain through countercurrent heat exchange with venous blood.